1. Field of the Invention
The present invention concerns antivibration/antishock devices. To be more precise, it concerns devices of the kind including a support member and a supported member joined together by damping means.
Damper devices of this kind are used to mount electric motors and internal combustion engines, air compressors and the like, and also to protect fragile or sensitive equipment against shock and vibration.
2. Description of the Prior Art
A prior art damper of this type is shown in figures 1a and 1b which are respectively an elevation view and a view in cross-section on the line X--X in figure 1a. It comprises a set of four substantially U-shape stainless steel blades received one within the other in pairs, the inside and outside blades of each pair of blades 10, 10', 11, 11' being respectively riveted to the corresponding blades of the other pair at their ends, to form a damper device 1 of approximately elliptical shape. In this example the fixing also uses respective attachment plates 12, 13 and 12', 13' covering the planes in which the blades are joined together and respective spacer plates 14 and 14' between the respective outside blades 10, 10' and inside blades 11, 11'.
The spaces between the respective outside blades 10, 10' and inside blades 11, 11' are filled with a damper substance 15 based on epoxy resin.
Bores 16 and 16' in the respective blades and plates are used to fix the object to be supported and to fix the damper device 1 to a base.
We have found that a damper device of this kind has a number of disadvantages.
First of all, epoxy resin has very poor heat resistance: around 0.degree. C. it is practically rigid, while at around 30.degree. C. it has a somewhat soft consistency.
As a result the resonant frequency of the damper device is highly temperature dependent, which is unthinkable for a device of this kind, since the aim is for it to have a given resonant frequency for a given supported mass.
Further, substances based on epoxy resins age badly and their service life is relatively limited. It is therefore necessary to replace damper devices incorporating such substances relatively frequently.
Moreover, a device of this kind is relatively complex to manufacture and consequently relatively costly.
We have considered replacing this type of damper device by another prior art type shown in FIGS. 2a through 2c which are respectively part-sectional, elevation and plan views of that device. The device 20 includes a bar 21 into a middle portion of which several runs of cable 22 are anchored, while the free ends of the cable 22 are each anchored in one of the elongate members 26 and 27. The elongate members 26 and 27 are held side by side in a plane parallel to the bar 21 by retaining means 28, the runs of cable 22 defining parallel curved cable segments 22 on opposite sides of the bar 21 and of the members 26 and 27.
Unfortunately, this type of damper device also has certain limitations.
If a compression load is applied to this damper device, it proves to be unstable in the horizontal direction: rather than moving only in a vertical direction (direction of the arrow A) it also moves horizontally (direction of the arrow B).
The present invention is aimed at alleviating these disadvantages.